Acute myocardial infarction is a major cause of morbidity and mortality in the United States, and continues to be the focus of major attempts at disease intervention. Since this condition is often precipitated by coronary artery thrombosis, timely dissolution of the fibrin clot can lead to both improved ventricular function and survival. The TIMI II clinical trial was established to determine the optimal regimen for tissue plasminogen activator (t-PA) intervention, along with beta blocker therapy and angioplasty. Our purpose is to outline the methods and procedures which we would use to provide laboratory testing support for the TIMI II trial, and to establish a sample repository for future work. The project has the following specific aims: 1) to develop dry anticoagulants and a vacuum tube blood collection system so that the appropriate samples may be obtained expeditiously under emergency room and coronary care unit conditions; 2) to assay these samples for t-PA antigen, fibrinogen, fibrin degradation products, plasminogen, and Alpha2-antiplasmin; 3) to apply more recent assays in selected patients; including, D-dimer fragment, B-beta fragments, t-PA inhibitor, fibrinopeptides A and B, factor V, factor VIII, and more sophisticated research assays for fragments of factors V, VII and VIII; 4) to establish a specimen repository for future analysis of blood related events associated with acute coronary occlusion and t-PA therapy. We believe our studies will provide critically important data for the correlation of changes in pertinent blood parameters with the primary and secondary end points of the TIMI trial: a) mortality and reinfarction; b) coronary artery reperfusion; and c) side effects such as bleeding. These correlations should ultimately lead to an optimized regimen for intervention with rt-PA in acute myocardial infarction.